What Are the 10 Most Addictive Substances?

Heroin 1 of 11

It's no surprise that heroin is probably the most addictive illegal drug, with at least 25% of people who have ever used it once becoming addicted. There are an estimated 50 million people who are regular users of this party drug across the globe, largely due to the euphoria experienced when it is injected. Unfortunately that euphoria is short-lived, and withdrawal effects can start as soon as two hours after your last dose of the drug. Many users are led down a dark road that never ends favorably.